After upgrading to Jenkins to  2.89.4 we noticed the throttle plugin 2.0.1 doesn't always prevent jobs from running in parallel as expected.

Steps to reproduce:
1. Create a Throttle category with

•  Maximum Total Concurrent Builds -> 0
• Maximum Concurrent Builds Per Node -> 3
• Maximum Concurrent Builds Per Node Labeled As Above -> 3.

2. Created Kubernetes Pod Template with

• Max number of instances -> 3
•  Container Cap -> 3

3. Create 3 jobs using the category, restricted to a node with two executors

4. Request builds of all 3 jobs.

What should happen:
4. Jobs run in sequence; 1 then 2 then 3.

What actually happens:
5. Job 1 starts building, jobs 2 and 3 wait in queue (OK).
6. After job 1 finishes, both job 2 and 3 start running (not OK).

Setup Details:

Jenkins :  2.89.4
Throttle Concurrent Builds : 2.0.1
Kubernetes : 1.3.1